1. Field of the Invention
This invention relates to a pushbutton-operated waveband or station selector and more particularly to improvements in a clutch mechanism to be provided between a core slide operatively connected to a memory plate slidable in response to pushing operation of each pushbutton and a manually-operated tuning knob.
2. Description of the Prior Art
There is a thin pushbutton-operated waveband or station selector wherein a pushbutton tuning portion is less than 1 cm thick. Such thin station selector is so arranged to shift a memory plate over a predetermined distance to a direction of the selector width by pushing a tuning pushbutton to cause front-rear movement of a core slide connected to the memory plate so that a tuning core mounted on the core slide enters in or gets out of a coil to perform tuning operation. A manually-operated tuning knob is further provided in addition to the tuning mechanism by pushbuttons for shifting the core slide in front-rear direction by rotating the tuning knob to select a station which is not set in pushbuttons or for doing fine adjustment upon tuning by pushbuttons.
However, if leaving the tuning knob and the core slide as being connected to each other, when a pushbutton is depressed, the memory plate comes to rotate the tuning knob, too, which means increase of load preventing smooth pushing operation of pushbuttons. In this connection, it has been proposed to provide a clutch mechanism between the tuning knob and the core slide so as to let out the clutch to reduce the load.
As stated above, a pushbutton-operated waveband or station selector comprises a tuner including cross arms for pushbuttons and a memory plate, a tuning section having tuning coils and a core slide, a manually-operated tuning knob and a clutch mechanism coupled with the tuning knob. Among those, the tuning section cannot be miniaturized smaller than a certain size due to sizes of tuning coils and cores for being inserted into the tuning coils or to inserting strokes of the cores. Pushbuttons and a memory plate operatively connected to the pushbuttons can today be made relatively thin. Therefore, in order to further miniaturize and thin such station selector, it is necessary to make small other portions, particularly its clutch mechanism. Additionally, on miniaturizing the clutch mechanism, special attention should be paid so that operational force from the tuning knob may surely be transmitted to the core slide, the cores may smoothly move and stop at determined positions inside the tuning coils. Further, when the pushbutton is depressed, the clutch has to be perfectly let out so that no load is applied from the tuning knob.
However, conventionally proposed clutch mechanisms include so many parts to prevent miniaturization and thinning thereof and to cause difficulty of mounting them. Further, in the conventional clutch mechanisms, there have often seen large loss of power transmission between tuning knobs and core slides to cause instability of shifting positions of cores inside tuning coils, resulting in frequency deviation during tuning operation.